The present invention relates to a contact image sensor.
There are two classes of contact type image sensors from the view point of their construction. The image sensors of one class is represented by illustration as shown in FIG. 1. The sensor of this type comprises a photosensor 10, a light source 12 provided extending parallel to the photosensor 10 and a lense 11 located so as to focus light rays emitted from the light source 12 and reflected on an original 1 to the photosensor 10. The size and weight of the image sensors of this type are increased by provision of the lense, as compared with those of the other class.
The operation of the image sensors of the other type may be understood from FIG. 3 which illustrates an embodiment but is explained here for the purpose of demonstration of the other type operation. In this construction, a photosensitive semiconductor device consisting of a pair of electrodes 3 and 5 and a semiconductor film 4 therebetween is formed on a glass substrate 2. A window is opened through the semiconductor device in order to allow light rays to pass therethrough from a light source 12 located behind the glass substrate 2 to the opposite side. A transparent insulating film 6 is coated over the photosensitive device. For operation, the device is placed on and makes contact with the surface of an original 1. Light rays are passed through the window 8, reflected in the original 1, and sensed by the semiconductor. However, a large number of manufacturing steps in photolithography are required for producing such devices and therefore production cost is increased.